1. Field of the Invention
This invention relates to electrical switches with current protection, such as circuit breakers, motor starters, motor controllers, transfer switches and the like, having communications connections for communicating with a remote station on a network, and alternatively, with a local portable unit.
2. Background Information
State of the art electrical switches with overcurrent protection, such as circuit breakers, motor staffers, motor controllers and transfer switches for example, utilize a microcomputer for performing various protection functions. The microcomputers in these devices also provide them with the capability of monitoring various parameters in the protected circuit, such as the current, power, energy, voltage, and, in some cases harmonic distortion and other parameters. Typically, such devices have incorporated manually operated switches for selecting various functions and parameter settings. In some instances, the individual units have been linked to a remote unit, at first through dedicated wiring and more recently through a network, for remote monitoring of the circuit breaker, and in some instances, for remotely operating the circuit breaker.
In a typical arrangement, the remote station is operated as a master station and the individual electrical switches are operated as slaves. In such an arrangement, the master station communicates with the individual devices over the network by sending messages uniquely addressed to the individual devices. The individual devices only reply to messages specifically addressed to them. In some instances, the master station may send a global message to all the stations which does not require a reply, such as a timing signal or a command to calculate power.
The switches for setting the various parameters on the electrical switches require room in the device as does a display for displaying the parameters and calculated values. There is a need for improved arrangement for setting and monitoring parameters and calculated values in microcomputer-based electrical switches which require less room in the device. At the same time there is a need for maintaining the integrity and security of the protection functions of the device.